The purpose of this project is to study the physical properties of a wide variety of biological macromolecules with the goal of correlating these properties to the structure and function of the macromolecules. The emphasis is on the thermodynamics of the interactions of these macromolecules and on their molecular size and shape. Analytical ultracentrifugation and mathematical modeling are the principal research techniques used. Studies on actin have been directed toward investigating the mechanisms involved in actin polymerization and the interaction of actin with actobindin. Studies on epidermal transglutaminase have involved characterization of the proenzyme form and study of the mechanism of activation. Studies on yeast arginase have been directed toward studying the reversible homogeneous association of this enzyme and the role of metal ions in controlling this. Studies of various deoxynucleotides have been directed toward investigating the reversible monomer-dimer equilibrium as a function of structure. Studies on alpha-helical fragments of keratin have been directed toward elucidating their role in keratin filaments. Studies on interleukin-2 receptors have been directed toward an elucidiction of the structure of the molecule. Studies on trypanosomatid proteins and tubulin and microtubules have been directed to an understanding of their interaction.